DE102010029930A1 - Preparing acetoacetoxyalkyl(meth)acrylate compounds, useful e.g. in adhesives, comprises reacting acetoacetic acid alkyl ester- with hydroxyalkyl(meth)acrylate-compounds in presence of catalyst and optionally in presence of stabilizer - Google Patents

Abstract

Preparing acetoacetoxyalkyl(meth)acrylate compounds (I), comprises reacting acetoacetic acid alkyl ester compounds with hydroxyalkyl(meth)acrylate compounds in the presence of catalyst(s) and optionally in the presence of stabilizer(s).

Description

The invention relates to a process for the preparation of acetoacetoxyalkyl (meth) acrylates.

Coating agents, in particular paints, have been produced synthetically for a long time. Many of these coating compositions are based on so-called alkyd resins, which are generally prepared using polybasic acids, alcohols and fatty acids and / or fatty acid derivatives. Many of these alkyd resins include organic solvents or dispersants to coat the resins in a thin layer on coating bodies. However, the use of these solvents should be omitted for reasons of environmental protection and occupational safety. Therefore, corresponding resins based on aqueous dispersions have been developed, but their storage stability is limited. Furthermore, the properties of many alkyd resins are not optimal. So the water intake is often too high. In addition, solvent resistance or hardness is too low for many applications.

Accordingly, attempts have been made to replace the previously outlined alkyd-based paints. For example, a solution polymer-based vinyl monomer-based coating composition is disclosed in U.S. Pat DE-A-101 06 561 described. However, this composition comprises a high proportion of organic solvents.

Furthermore, aqueous dispersions based on meth) acrylate polymers are also known. For example, the document describes DE-A-41 05 134 aqueous dispersions which can be used as binders in paints. The preparation of these binders, however, takes place over several stages, wherein initially a solution polymer is produced, which is used after a neutralization in an emulsion polymerization.

In addition, in DE-A 25 13 516 aqueous dispersions comprising polymers based on (meth) acrylates, wherein a part of the (meth) acrylates is derived from unsaturated alcohol radicals. A disadvantage of the described dispersions is in particular their complicated preparation, wherein the polymers based on (meth) acrylates are obtained by solution polymerization. In this case, these polymers have a high proportion of acid groups, which is in the range of 5 to 20 wt .-%, based on the solution polymer.

The publication DE-A-26 38 544 describes oxidatively drying aqueous dispersions which comprise emulsion polymers based on (meth) acrylates, some of the (meth) acrylates used being derived from unsaturated alcohol radicals. However, chain transfer agents have been used to prepare the emulsion polymers so that emulsion polymer shows high solubility.

Furthermore, aqueous dispersions comprising oxidatively drying polymers in F.-B. Chen, G. Bufkin, "Crosslinkable Emulsion Polymers by Autooxidation II", Journal of Applied Polymer Science, Vol. 30, 4551-4570 (1985). explained. The polymers contain from 2 to 8% by weight of units derived from (meth) acrylates having unsaturated, long-chain alcohol radicals. However, these polymers do not contain units obtained by polymerization of acid group-containing monomers. The durability of these dispersions and the hardness of the coatings are not sufficient for many applications.

Acetoacetoxyethyl methacrylate (AAEM) is widely described in the literature. It is used in water-based acrylate emulsions that are suitable for coatings and coatings. The reactive components of this compound are particularly advantageous for the crosslinking reactions of the curing process of paints. In addition, this compound has a good metal adhesion. Thus, it is also found in adhesive applications.

From the EP 0 555 774 is a one-step process for the preparation of aqueous, self-crosslinking copolymer dispersions based on acetoacetyl- and carboxyl-containing acrylate copolymers which are neutralized with acting as a crosslinking component polyamines are known.

In the EP 0794970 describes a two-stage process for the preparation of such copolymer dispersions. In this case, the proportion of acetoacetyl groups is reduced in order to prevent the formation of specks and coagulum occurring during the copolymerization. Films of aqueous copolymer dispersions with small amounts of acetoacetyl groups which have a high crosslinking density when the emulsion copolymerization is carried out by a two-stage process are used, with acetoacetyl- or carboxyl-containing monomers being used only in the first stage.

EP 0 808 822 describes a process for the preparation of malonate group-containing acrylate monomers. It describes the reaction of hydroxyl-containing acrylic monomers with an excess of dialkylmalonate in the presence of a catalyst and a polymerization inhibitor while passing a gas for heating. During the heating step, the by-produced alcohol is removed from the system.

For the preparation of acetoacetoxyethyl (meth) acrylate, the synthesis of 2-hydroxyethyl methacrylate with diketene is described in the prior art. Diketen is very poisonous and extremely reactive. For the synthesis of acetoacetoxyethyl (meth) acrylate, therefore, the precursor, the diketene, must be prepared on site, since it is not transport stable. In the JP 07047614 the acetoacetoxyethyl (meth) acrylate is obtained in the reaction of diketene with 2-hydroxyethyl methacrylate in the presence of dibutyltin dilaurate and p-benzoquinone in a purity of 95%.

The notation (meth) acrylate here means both methacrylate, such as. As methyl methacrylate, ethyl methacrylate, etc., as well as acrylate, such as. As methyl acrylate, ethyl acrylate, etc., as well as mixtures of the two.

It was therefore an object to provide a process for the preparation of acetoacetoxyalkyl (meth) acrylates which can be carried out with transport-stable and non-toxic starting materials and, moreover, gives high yields.

wobei
A für lineare oder verzweigte Alkylgruppen steht mit 2 bis 6 C-Atomen, die ggf. substituiert sein können und
Alk für lineare oder verweigte Alkylgruppen steht mit 1 bis 5 C-Atomen.The task was solved by implementations of the kind:

in which
A is a linear or branched alkyl group having 2 to 6 carbon atoms, which may be optionally substituted and
Alk represents linear or branched alkyl groups having 1 to 5 C atoms.

Surprisingly, acetoacetoxyalkyl (meth) acrylates can be obtained by the process according to the invention with high conversion. The starting materials alkyl acetoacetate and hydroxyalkyl (meth) acrylate are not toxic and stable. They are widely available in the trade and can be processed without special safety precautions.

All suitable alkyl acetoacetates may be used, preferably methyl acetoacetate and ethyl acetoacetate.

For the hydroxyalkyl (meth) acrylates, a variety of commercially available compounds are available. Hydroxyethyl methacrylate (HEMA) and hydroxypropyl methacrylate (HPMA) are particularly preferably used.

Suitable transesterification catalysts are a.) Brønstedt acids, such as, for example, sulfuric acid, para-toluenesulfonic acid, acidic ion exchangers or a combination thereof with metals such as zinc oxide; b.) bases, in particular metal alkoxides, especially alkoxides of lithium, sodium or potassium, such as LiOCH ₃ , NaOCH ₃ , KOCH ₃ , the corresponding acetates, propionates or butanolates; but also aluminum compounds, such as aluminum isopropionate; Carbonates, such as K ₂ CO ₃ ; Hydroxides such as LiOH, NaOH, Ca (OH) ₂ ; basic oxides, such as CaO; basic ion exchangers; Ammonia; Metal amides such as LiNH ₂ or NaNH ₂ ; Amines such as primary, secondary or tertiary amines, such as triethylamine, diisopropylethylamine; or particularly strong amines, such as 4- (dimethylamino) pyridine (DMAP) or 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU; to be used together with LiBr); and c.) Lewis acids or metal oxides, in particular titanium, zirconium or tin catalysts, such as isopropyl titanate, isobutyl titanate, titanium hydroxide, titanium dioxide, dioctyltinoid, dibutyltin oxide, tributyltin alcoholates, dibutyltin dialcoholates; dibutyl; Titanium tetraalcoholates, titanium tetrachloride or mixed forms such as Ti (OEt) ₄ , Ti (OEt) ₄ -n (OMe) n, Ti (Oi-Pr) ₃ Cl or Ti (Oi-Pr) ₂ Cl ₂ ; but also other metal compounds, such as i-PrOCu (PPh) ₃ , palladium catalysts can be used. Alternatively, suitable enzymes for transesterification can also be used for this purpose. A variety of useful transesterification and transesterification methods are included Otera (Chem. Rev., 93, 1993, pp. 1449-70) described.

Hydrogen phosphates, preferably potassium dihydrogen phosphate and / or sodium dihydrogen phosphate or mixtures thereof, are used according to the invention as catalysts.

The catalysts are used in amounts of from 1 to 10% by weight, based on the amount of hydroxyalkyl methacrylate used.

The reaction mixture may be added to stabilizers which prevent radical polymerization of the (meth) acrylic groups during the reaction. These inhibitors are well known in the art.

worin
R⁵ einen linearen oder verzweigten Alkylrest mit eins bis acht Kohlenstoffatomen, Halogen oder Aryl bedeutet, vorzugsweise einen Alkylrest mit eins bis vier Kohlenstoffatomen, besonders bevorzugt Methyl, Ethyl, n-Propyl, iso-Propyl, n-Butyl, iso-Butyl, sec-Butyl, tert.-Butyl, Cl, F oder Br;
o eine ganze Zahl im Bereich von eins bis vier, vorzugsweise eins oder zwei ist; und
R⁶ Wasserstoff, einen linearen oder verzweigten Alkylrest mit eins bis acht Kohlenstoffatomen oder Aryl bedeutet, vorzugsweise einen Alkylrest mit eins bis vier Kohlenstoffatomen, besonders bevorzugt Methyl, Ethyl, n-Propyl, iso-Propyl, n-Butyl, iso-Butyl, sec-Butyl oder tert.-Butyl.Are used mainly 1,4-dihydroxybenzenes. However, it is also possible to use differently substituted dihydroxybenzenes. In general, such stabilizers can be represented by the general formula (a)

wherein
R ^{5 is} a linear or branched alkyl radical having one to eight carbon atoms, halogen or aryl, preferably an alkyl radical having one to four carbon atoms, more preferably methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec Butyl, tert -butyl, Cl, F or Br;
o is an integer in the range of one to four, preferably one or two; and
R ^{6 is} hydrogen, a linear or branched alkyl radical having one to eight carbon atoms or aryl, preferably an alkyl radical having one to four carbon atoms, particularly preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec Butyl or tert-butyl.

worin
R⁵ einen linearen oder verzweigten Alkylrest mit eins bis acht Kohlenstoffatomen, Halogen oder Aryl bedeutet, vorzugsweise einen Alkylrest mit eins bis vier Kohlenstoffatomen, besonders bevorzugt Methyl, Ethyl, n-Propyl, iso-Propyl, n-Butyl, iso-Butyl, sec-Butyl, tert.-Butyl, Cl, F oder Br; und
o eine ganze Zahl im Bereich von eins bis vier, vorzugsweise eins oder zwei ist.However, it is also possible to use compounds with 1,4-benzoquinone as the parent compound. These can be described by the formula (b)

wherein
R ^{5 is} a linear or branched alkyl radical having one to eight carbon atoms, halogen or aryl, preferably an alkyl radical having one to four carbon atoms, more preferably methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec Butyl, tert -butyl, Cl, F or Br; and
o is an integer in the range of one to four, preferably one or two.

worin
R⁵ einen linearen oder verzweigten Alkylrest mit eins bis acht Kohlenstoffatomen, Aryl oder Aralkyl, Propionsäureester mit 1 bis 4 wertigen Alkoholen, welche auch Heteroatome wie S, O und N enthalten können, vorzugsweise einen Alkylrest mit eins bis vier Kohlenstoffatomen, besonders bevorzugt Methyl, Ethyl, n-Propyl, iso-Propyl, n-Butyl, iso-Butyl, sec-Butyl, tert.-Butyl bedeutet.Likewise phenols of the general structure (c) are used

wherein
R ^{5 is} a linear or branched alkyl radical having one to eight carbon atoms, aryl or aralkyl, propionic acid esters having 1 to 4 valent alcohols, which may also contain heteroatoms such as S, O and N, preferably an alkyl radical having one to four carbon atoms, particularly preferably methyl, Ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl.

mit R⁷ = Verbindung der Formel (e)

worin R⁸ = C_pH_2p+1 mit p = 1 oder 2 ist.Another advantageous class of substances are hindered phenols based on triazine derivatives of the formula (d)

with R ⁷ = compound of the formula (e)

wherein R ⁸ = C _p H _{2p + 1} with p = 1 or 2.

Particularly successful are the compounds 1,4-dihydroxybenzene, 4-methoxyphenol, 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone, 1,3,5-trimethyl-2,4,6-tris ( 3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 2,6-di-tert-butyl-4-methylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,2-bis [3, 5-bis (1,1-dimethylethyl) -4-hydroxyphenyl-1-oxopropoxymethyl)] 1,3-propanediyl ester, 2,2'-thiodiethyibis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) ] propionate, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3,5-bis (1,1-dimethylethyl-2,2-methylenebis (4-methyl-6-tert .butyl) phenol, tris- (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) -s-triazine-2,4,6- (1H, 3H, 5H) trione, tris (3,5-) di-tert-butyl-4-hydroxy) -s-triazine-2,46- (1H, 3H, 5H) trione or tert-butyl-3,5-dihydroxybenzene.

Particularly preferred stabilizers hydroquinone monomethyl ether and / or 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl (TEMPOL), phenothiazine, phenylenediamine derivatives and / or Kupferdialkyldithiocarbamate be used.

Based on the weight of the total reaction mixture 0.0005 to 0.1 wt .-% stabilizers are added.

The alkyl acetoacetate is used in a molar excess of from 3: 1 to 7: 1, preferably 4: 1 to 5: 1, based on the particular hydroxyalkyl (meth) acrylate.

The alkyl acetoacetate is initially charged with the novel catalyst or catalyst mixture and optionally with the stabilizers or stabilizer mixtures described. Under vacuum between 100 and 1000 mbar and a temperature between 80 ° C and 120 ° C (depending on the pressure), the respective hydroxyalkyl (meth) acrylate is added while introducing air. It is worked at the boiling point of the reaction mixture to remove the resulting alcohol in the reaction continuously by distillation. Excess alkyl acetoacetate is distilled off under reduced pressure, if appropriate under atmospheric pressure and elevated temperature.

Since the acetoacetoxyalkyl (meth) acrylates have good storage stability, they can be fed to a wide variety of applications.

Acetoacetoxyalkyl (meth) acrylates may be used as components of paint systems, e.g. B. can be used as a reactive diluent, in particular for crosslinking.

The acetoacetoxyalkyl (meth) acrylates can also be used as comonomer for polymerization reactions.

Of particular interest is the copolymerization of acetoacetoxyalkyl (meth) acrylates, since these polymer blends can be postcrosslinked via Michael reactions.

The crosslinking of acetoacetoxyalkyl (meth) acrylates with diamines is inter alia J. Feng et al. in the Journal of Coatings Technology, Vol. 70, No. 881, pp. 57-68 described.

The crosslinking of acetoacetoxyalkyl (meth) acrylates with polyhydrazines, in particular with adipic dihydrazide, is described in US Pat US 4988762 described.

The acetoacetoxyalkyl (meth) acrylates can also be reacted with melamine resins or with isocyanates.

Acetoacetoxyalkyl (meth) acrylates can also be used in adhesives.

The following example is given to better illustrate the present invention, but is not intended to limit the invention to the features disclosed herein. example

Approach:

• 174.18 g (1.5 mol) of methyl acetoacetate
• 65.07 g (0.5 mol) of 2-hydroxyethyl methacrylate,
• 0.054 g (500 ppm b.a., product) of hydroxyquinone monomethyl ether
• 0.005 g (50 ppm b.a., product) 4-hydroxy-2,2,6,6-tetramethylpipiridinooxyl (TEMPOL)
• 2.76 g (4.25% b.a., 2-hydroxyethyl methacrylate) potassium dihydrogen phosphate (equivalent to 0.021 mol)

In a four-necked round bottomed flask, methyl acetoacetate, stabilizers and catalyst are presented. The apparatus is evacuated (500 mbar) and heated to 100 ° C. with stirring and introduction of air. At this temperature and 500 mbar, the 2-hydroxyethyl methacrylate is added dropwise within 2 h and then the resulting methanol distilled off.

The reaction mixture is heated at 500 mbar to 100 ° C and the excess methyl acetoacetate distilled off while constantly reducing the pressure (up to 4 mbar).

After cooling to room temperature, the product is filtered through a 500 mL Seitz pressure filter (filter layer: T100) (filtration: 0.3 bar).

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10106561 A [0003]
• DE 4105134A [0004]
• DE 2513516 A [0005]
• DE 2638544 A [0006]
• EP 0555774 [0009]
• EP 0794970 [0010]
• EP 0808822 [0011]
• JP 07047614 [0012]
• US 4988762 [0037]

Cited non-patent literature

• F.-B. Chen, G. Bufkin, "Crosslinkable Emulsion Polymers by Autooxidation II", Journal of Applied Polymer Science, Vol. 30, 4551-4570 (1985) [0007]
• Otera (Chem. Rev., 93, 1993, pp. 1449-70) [0019]
• J. Feng et al. in the Journal of Coatings Technology, Vol. 70, No. 881, pp. 57-68 [0036]

Claims (4)

Process for the preparation of acetoacetoxyalkyl (meth) acrylates, characterized in that alkyl acetoacetates are reacted with hydroxyalkyl (meth) acrylates in the presence of a catalyst or catalyst mixture and optionally in the presence of a stabilizer or stabilizer mixture. Process according to Claim 1, characterized in that alkyl acetoacetate is reacted in a molar excess of from 3: 1 to 7: 1, based on the particular hydroxyalkyl (meth) acrylate. A method according to claim 1, characterized in that the reaction is carried out in the presence of hydrogen phosphates. A method according to claim 1, characterized in that the reaction is carried out in the presence of hydroquinone monomethyl ether and / or 4-hydroxy-2,2,6,6-tetramethylpipiridinooxyl.